The present invention relates, generally, to a diffusion sheet for use in a backlight unit of a TFT-LCD (Thin Film Transistor-Liquid Crystal Display), and, more particularly, to a diffusion sheet for a display, which can uniformly diffuse light, which is radiated from a light source lamp positioned at a side surface or the back surface of the display, while passing such light therethrough, to thus obtain clear display images.
Recently, LCDs are variously used not only as monitors for notebook computers but also as large monitors for desktop computers and monitors for television sets. Accordingly, the need for screens to be large and the luminance to be high of backlight units, serving as the light source of LCDs, is increasing. In the backlight unit, a diffusion sheet functions to diffuse light from the light source at the side surface or back surface of the display to the entire screen and to uniformly transfer such light forward by means of refraction. The backlighting process is an indirect lighting process for enhancing the brightness of a display screen in a manner such that light originating from the light source of a backlight unit, mounted to the back surface of a display, is transferred to the opposite side through a light guide plate and then reflected at a reflective plate, such as a metal deposition plate or an opaque white plate, to radiate the light forward. Thereby, the backlighting process is a light emission technique that is able to overcome the problems with the conventional front-lighting process. In the backlighting process, when the number of light sources of a backlight unit is increased in order to realize high image brightness, power consumption and heat generation rates are increased. However, since maximum light efficiency should be realized using minimum power consumption, typical techniques of manufacturing a light-diffusion sheet comprising a base sheet and a light-diffusing layer formed on at least one surface of the base sheet in order to transfer light from a light source to a liquid crystal operator have been proposed. As such, in the light-diffusion sheet, it is important to realize an efficient design for the light-diffusing layer formed on the base sheet and to improve the functions thereof through such a design.
In this regard, Japanese Patent Application No. 2002-104820 discloses a light-diffusing layer which is formed of a resin film having fine roughness on at least one surface of a transparent film. As such, this patent is characterized in that the transparent film contains a thermoplastic resin having a substituted and/or unsubstituted imido group on a side chain thereof and a thermoplastic resin having a substituted and/or unsubstituted phenyl group and a nitrile group on a side chain thereof. In addition, Korean Patent Application No. 1996-38912 discloses a method of forming a layer of a transparent resin and organic particles on a transparent plastic sheet to increase light efficiency and luminance. However, such conventional techniques suffer because they are difficult to use to actually realize high luminance and shielding of LCDs, that is, improved total light transmittance and light diffusibility, merely by varying the combination of resin and particles applicable in the light-diffusing layer.